Streptococcus infantarius
Cultural characteristics
Biochemical characters
Phylum Firmicutes, Class Bacilli, Order Lactobacillales, Family Streptococcaceae, Genus Streptococcus, Streptococcus infantarius  
Schlegel et al. 2000. Lancefield group D or non-groupable (approximately 40% of strains carry the Lancefield group D antigen).

Note: in their work Schlegel et al. proposed 2 subspecies infantarius and coli, but S. infantarius subsp. coli was not validly published because no type
strain was designated. In 2002 Poyart et al. included one strain of Schlegel's subspecies
coli in S. lutetiensis.  In 2003 Schlegel et al.  describe again the
Streptococcus infantarius subsp. coli and Streptococcus infantarius subsp. infantarius but type strain is erroneously cited.
Gram-positive cocci, nonmotile, nonsporulated, grouped in pairs and short chains.
Colonies on blood agar are circular, 1 mm in diameter after 24 h incubation at 37 ºC,
unpigmented and alpha-hemolytic. Growth temperature 37 ºC. Facultatively
anaerobic. Growth is enhanced in a 5% CO
2 atmosphere. Grow on Trypticase soy
agar with 5% horse / sheep blood, Brain heart infusion agar or broth, MRS broth. No
growth occurs in 6.5% NaCl broth.
Isolated from human feces, clinical specimens (blood, urine) & foods. (Rarely encountered)
One case of endocarditis.
Possible association of
S. infantarius with noncolonic digestive cancers.
  1. Schlegel L., Grimont F., Collins M.D., Regnault B., Grimont P.A.D. &  Bouvet A.: Streptococcus infantarius sp. nov., Streptococcus
    infantarius subsp. infantarius subsp. nov. and Streptococcus infantarius subsp. coli subsp. nov., isolated from humans and food.
    Int. J. Syst. Evol. Microbiol., 2000, 50, 1425-1434.
  2. Poyart C., Quesne G. & Trieu-Cuot P.: Taxonomic dissection of the Streptococcus bovis group by analysis of manganese-
    dependent superoxide dismutase gene (sodA) sequences: reclassification of 'Streptococcus infantarius subsp. coli' as
    Streptococcus lutetiensis sp. nov. and of Streptococcus bovis biotype II.2 as Streptococcus pasteurianus sp. nov. Int. J. Syst. Evol.
    Microbiol., 2002, 52, 1247-1255.
  3. Schlegel L., Grimont F., Ageron E., Grimont P.A.D. &  Bouvet A.: Reappraisal of the taxonomy of the Streptococcus
    bovis/Streptococcus equinus complex and related species: description of Streptococcus gallolyticus subsp. gallolyticus subsp.
    nov., S. gallolyticus subsp. macedonicus subsp. nov. and S. gallolyticus subsp. pasteurianus subsp. nov. Int. J. Syst. Evol.
    Microbiol., 2003, 53, 631-645.
  4. Corredoira J, Alonso MP, Coira A, Varela J.: Association between Streptococcus infantarius (formerly S. bovis II/1) bacteremia and
    noncolonic cancer. J Clin Microbiol. 2008 Apr;46(4):1570.
  5. Robert A. Whiley and Jeremy M. Hardie, 2009. Genus I. Streptococcus Rosenbach 1884, 22AL. In: (Eds.) P.D. Vos, G. Garrity, D.
    Jones, N.R. Krieg, W. Ludwig, F.A. Rainey, K.-H. Schleifer, W.B. Whitman. Bergey’s Manual of Systematic Bacteriology, Volume 3:
    The Firmicutes, Springer, 655-711.
Positive results for alpha-galactosidase, Voges-Proskauer reaction, leucine
aminopeptidase, alanylphenylalanyl-proline arylamidase, acid production from:
lactose, maltose, melibiose & sucrose.

Negative results for arginine dihydrolase, alkaline phosphatase, catalase, N-acetyl-beta-glucosaminidase, beta-galactosidase,
beta-glucuronidase, glycyl-tryptophan arylamidase, beta-glucosidase, methyl beta-D-glucopyranoside, hippurate hydrolysis,
beta-mannosidase,  pyrrolidonylarylamidase, urease, acid production from: arabinose, arabitol, cyclodextrin, inulin, D-mannitol,
melezitose, ribose, sorbitol, D-tagatose & trehalose.

Variable results for esculin hydrolysis, acid production from: glycogen, melibiose, methyl beta-D-glucopyranoside, pullulan,
D-raffinose & starch.
(c) Costin Stoica
Culture media
Biochemical tests
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